Chess, the great game of simulated warfare, has existed for 1500 years and, according to science fiction, will command humanity's intellectual attraction for at least hundreds more. Standard chess is plenty of fun, but why not mix it up? Here are twelve variations of the game that you might not know about.

1. 3RD Millennium Chess is played on a single board, but one that's been wrapped into a cylinder. To make it even more complex, knights can move in tandem. Players can move both knights together at the same time on the same square or split them apart for independent movement.

2. Chess Cubic, invented by Robert Bell, wraps a 96-square board around a cube. Kings, queens and bishops are sheltered by pawns, rooks and knights. Pawns are given two different colors to distinguish their directions of movement.

3. Rollerball Chess got its name from the dystopian science fiction movie of the same name. This variant, invented by Jean-Louis Cazaux in 1998, gives each side 2 pawns, 1 king, 2 rooks and 1 bishop. They move on a board resembling a rollerskating rink.

4. Atomic Chess updates this ancient game of war with the deadliest weapons modern technology can build. Captures--all of them--result in atomic explosions which kill all other pieces in the eight surrounding squares. It can turn into a war of annihilation: if both kings are killed simultaneously in an atomic explosion, the remaining pieces must fight to the death.

5. The object of the game in Suicide Chess is to lose all of your pieces first. Capturing available opposing pieces is mandatory, so avoid a position of strength.

6. Quantum Chess is a computer-driven variant in which the type of each piece is in a constant state of flux. Is this piece a rook, a bishop or something else? It varies:

In the quantum chess computer game created by undergraduate computer science student Alice Wismath, a piece that should be a knight could simultaneously also be a queen, a pawn or something else. The player doesn't know what the second state might be or which of the two states the piece will choose when it is moved.[...]

Wismath also chose new rules to make the game workable with its quantum twist. For example, her version of quantum chess requires a player to capture the king, which never changes to another piece, instead of merely delivering a checkmate. Also, pieces change states only when they land on black squares.

7. The people are revolting! In Peasant Revolt,the pawns have risen up in rebellion against the aristocracy. One side has a king and eight pawns. The other has a king, three knights and a single, loyal pawn.

8. In Stealth Bomber Chess, invented by Jeremy Harper, one pre-selected piece is a suicide bomber. The player may, instead of moving during a turn, detonate the bomb, killing all pieces, except kings, in the eight adjoining squares.

9. Chess Boxing is the ultimate test of body and mind. This sport consists of alternating rounds of chess and boxing. A checkmate or a knockout results in a win:

Chessboxers go through alternating four-minute long rounds of chess and three-minute boxing rounds with a one-minute break in between. A maximum total of 11 rounds are fought out—six rounds of chess and five rounds of boxing. The fight begins with a round of chess. Each player has a respite of 12 minutes during the game of chess, which means the maximum duration of the whole chess game is 24 minutes. A K.O. or checkmate can lead to an early win, and the fight can also be cut short if a player exceeds the chess time limit or the referee decides the fight has to be aborted. If the game of chess ends with a tie, it is settled with the points earned in the boxing rounds. If the boxing fight ends with a tie, the player who had black on the chessboard wins.

10. In Cannibal Chess, one piece that captures another acquires the movement abilities of the captured piece. And, presumably, the victorious player is required to eat his opponent.

11. Bughouse Chess consists of four players divided into two teams. When one player captures an enemy piece, he gives it to his partner, who can then place it on own board as a friendly piece.

12. Three-Dimensional Chess is perhaps the mostly widely known variant, thanks to its frequent appearance on Star Trek. Fans have made functional rules for this multi-layered game--a most logical choice.

You left off the rather deadly variant featured in the Doctor Who episode Closing Time. As pieces are moved, they acquire an electrical charge. So if your game is too dependent on any one piece (i.e. the queen) you'll reach a point where you can move that piece, you really need to move that piece, but doing so will kill you. LOL